8.2.1 Design Requirements

TUSB211A requires a valid reset signal as described in the Power Supply Recommendations section. The

capacitor at RSTN pin is not required if a micro controller drives the RSTN pin according to recommendations.

For this design example, use the parameters provided in Table 8-1.

Table 8-1. Design Parameters for 3.3-V Supply With Low to Medium Loss System

PARAMETER

VALUE(1)

VCC

3.3 V ±10%

I2C support required in system (Yes/No)

No

Edge and DC Boost

REQ

EQ Level

EQ Level 0:

REQ = 0-Ω

0-Ω

0

1.8 kΩ ±1%

1

3.6 kΩ ±1%

2

Do Not Install (DNI)

3

(1)

These parameters are starting values for a low to medium loss system. Further tuning might be required based on specific host or

device as well as cable length and loss profile. These settings are not specific to a 3.3-V supply system and could be applicable to 5-V

supply system as well.

8.2.2 Detailed Design Procedure

The ideal EQ setting is dependent upon the signal chain loss characteristics of the target platform. The

recommendation is to start with EQ Level 0, and then increment to EQ Level 1, and so on.

For the TUSB211A to recognize any change to the EQ setting, the RSTN pin must be toggled. This is because

the EQ pin is latched on power up and the pin is ignored thereafter.

Placement of the device is also dependent on the application goal. Table 8-2 describes TI recommendations.

Table 8-2. Platform Placement Guideline

PLATFORM GOAL

SUGGESTED TUSB211A PLACEMENT

Pass USB Near End Mask at the receptacle

Close to measurement point (connector)

Pass USB Far End Eye Mask at the plug

Close to USB PHY

Cascade multiple TUSB211As to improve device enumeration

Midway between each USB interconnect

Table 8-3. Table of Recommended Settings

EQ settings(1) for channel loss

Pre-channel cable length (Between USB PHY and TUSB211A)

EQ

0-3 meter

Level 0

2-5 meter

Level 1

Post-channel cable length (Between TUSB211A and inter-connect)

EQ

0-2 meter

Level 0

1-4 meter

Level 1

(1)

These parameters are starting values for different cable lengths. Further tuning might be required based on specific host or device as

well as cable length and loss profile.

8.2.2.1 Test Procedure to Construct USB High-Speed Eye Diagram

Note

USB-IF certification tests for High-speed eye masks require the mandated use of the USB-IF

developed test fixtures. These test fixtures do not require the use of oscilloscope probes. Instead

they use SMA cables. More information can be found at the USB-IF Compliance Updates Page. It is

located under the Electrical Specifications section, ID 86 dated March 2013.

TUSB211A

SLLSFW2 – SEPTEMBER 2023

www.ti.com

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